In response to infection, numerous cell types within the vertebrate immune system act in concert to effect the rapid and efficient clearance of the invading pathogen. Among these cell types are T cells, which develop in the thymus and which are responsible for cell-mediated immunity. T cells are divided into several major subclasses, including cytotoxic T cells, which kill virus-infected cells, as well as two classes of regulatory cells, called helper T cells (Th cells) and suppressor T cells, which act to modulate the activity of other immune cells. During chronic infections, helper T cells develop into at least two phenotypically and functionally distinct effector populations, Th1 and Th2 lymphocytes. Th1 cells produce IFN-xcex3 and IL-2, which are commonly associated with cell-mediated immune responses against various intracellular pathogens, whereas Th2 cells produce cytokines such as IL-4, IL-5, IL-6, IL-10 and IL-13, which are crucial to control extracellular helminthic infections.
In certain cases, the number, activity, or other properties of Th1 or Th2 cells can become abnormal, and these cell types can play a role in one or another disease or condition. For example, Th1 cells have been associated with organ-specific autoimmune diseases, delayed-type hypersensitivity, and transplant rejection. In addition, imbalance of Th2 cytokines are observed in various atopic and allergic diseases, which are usually accompanied by increased production of IgG1 and IgE as well as the activation of eosinophils and mast cells.
Cytokines such as IL-12 and IL-4 have dominant roles in determining the outcome of Th differentiation into Th1 and Th2 subsets, respectively. These cytokines bind to their cognate receptors, leading to activation of the Janus family of kinases (JAKs) and the latent transcription factors known as signal transducers and activators of transcription (STATs). For example, in Th1 cells, following the binding of IL-12 to its cognate receptor, STAT4 is activated, thereby leading to the production of IFN-xcex3. Accordingly, STAT4-deficient mice are defective in Th1 differentiation and do not respond to intracellular pathogens such as Listeria monocytogenes. In Th2 cells, IL-4 leads to the activation of STAT6, which is essential for the development of these cells. Accordingly, STAT6-deficient mice have an impaired ability to produce IL-4-secreting Th2 cells, thereby resulting in a failure to expel intestinal helminths. Interestingly, these STAT6 mutant mice are protected from antigen-induced airway hyperresponsiveness.
Additional reports have identified various genes that are differentially expressed in Th1 and Th2 cells. For example, the transcription factor ERM is selectively expressed in Th1 cells, and, in Th2 cells, GATA-3 and c-Maf are selectively expressed. GATA-3 is required for the expression of certain Th2 specific genes, can lead to the expression of IL-4 and IL-5 in Th1 cells, and inhibits the production of IFN-xcex3 in Th1 cells. See, e.g., Zheng and Flavell (1997) Cell 89(4):587-96; Zhang et al., (1997) J. Biol. Chem. 272:21597-603; or Ferber et al., (1999) Clin. Immunol. 91:134-144. Additionally, several cell surface proteins are also differentially expressed in the Th1 and Th2 subsets. For example, Th1 cells express various chemokine receptors such as CXCR3, CCR1, and CCR5. Th2 cells, in contrast, express CD30 as well as various chemokine receptors such as CCR8.
Various cell surface proteins have been identified as having four-transmembrane domains, and are called tetraspanins, or transmembrane 4 superfamily (TM4SF). Such proteins, including, for example, CD81, CD9, and CD20, have a strong propensity to form molecular associations with other cell surface molecules. CD81, for example, which is expressed in both T and B lymphocytes, is found in a multimolecular complex with CD19 and the complement receptors 1 and 2 in B lymphocytes. Previous studies have demonstrated that this complex collectively regulates the threshold for antigen receptor-mediated B cell activation. In T cells, CD81 contributes to cell proliferation as well as to IL-2 and IL-4 production. Other four transmembrane proteins have been associated with various cellular activities, including receptor activity, cell-cell binding, integrin binding and/or signaling, or channel activity, e.g., Ca2+ channel activity (see, e.g., Bubien et al., (1993) J Cell Biol 121(5):1121-32).
The present invention provides nucleic acids encoding a novel Th1 cell-specific protein, Chandra. The herein-disclosed sequences can be used for any of a number of purposes, including for the specific detection of Th1 lymphocytes, for the identification of molecules that associate with and/or modulate the activity of Chandra, to diagnose any of a number of conditions associated with Th1 or Th2 cell activity, or to modulate the number and/or activity of Th1 or Th2 lymphocytes in a mammal.
In one aspect, the present invention provides isolated nucleic acids encoding a Th1-associated polypeptide, the polypeptide comprising at least about 70% amino acid sequence identity to SEQ ID NO:1.
In one embodiment, the polypeptide specifically binds to polyclonal antibodies generated against a polypeptide having an amino acid sequence of SEQ ID NO:1. In another embodiment, the polypeptide comprises an amino acid sequence of SEQ ID NO:1. In another embodiment, the nucleic acid hybridizes under moderately stringent hybridization conditions to a nucleic acid comprising a nucleotide sequence of SEQ ID NO:2. In another embodiment, the nucleic acid hybridizes under stringent hybridization conditions to a nucleic acid comprising a nucleotide sequence of SEQ ID NO:2.
In another aspect, the present invention provides an expression cassette comprising a nucleic acid encoding a ThI-associated polypeptide, the polypeptide comprising at least about 70% amino acid sequence identity to SEQ ID NO:1.
In another aspect, the present invention provides an isolated cell comprising the expression cassette.
In another aspect, the present invention provides an isolated polypeptide comprising at least about 70% amino acid sequence identity to SEQ ID NO:1.
In one embodiment, the polypeptide specifically binds to polyclonal antibodies generated against a polypeptide comprising an amino acid sequence of SEQ ID NO:1. In another embodiment, the polypeptide comprises an amino acid sequence of SEQ ID NO:1.
In another aspect, the present invention provides antibodies that specifically bind to a polypeptide comprising at least about 70% amino acid sequence identity to SEQ ID NO:1.
In another aspect, the present invention provides a method of identifying a compound that modulates Th1 cell activity or differentiation, the method comprising: (1) contacting a Th1-associated polypeptide with a compound, wherein the polypeptide comprises at least about 70% amino acid sequence identity to SEQ ID NO:1; and (2) determining the functional effect of the compound on the polypeptide.
In one embodiment, the polypeptide is expressed within a cell or a cell membrane. In another embodiment, the compound increases the activity of the polypeptide. In another embodiment, the compound decreases the activity of the polypeptide.
In another aspect, the present invention provides a method of treating a disease or a condition associated with Th1 cell activity in a patient, the method comprising administering to the patient a compound that decreases the activity of a Th1-associated polypeptide, the polypeptide comprising at least about 70% amino acid sequence identity to SEQ ID NO:1.
In a preferred embodiment, the compound is identified by (1) contacting the polypeptide with a compound, and (2) determining the functional effect of the compound on the polypeptide.
In one embodiment, the disease or condition is an autoimmune disease or transplant rejection.
In another aspect, the present invention provides a method of treating a disease or a condition associated with Th2 cell activity in a patient, the method comprising administering to the patient a compound that increases the activity of a Th1-associated polypeptide, the polypeptide comprising at least about 70% amino acid sequence identity to SEQ ID NO:1.
In a preferred embodiment, the compound is identified by (1) contacting the polypeptide with a compound, and (2) determining the functional effect of the compound on the polypeptide.
In one embodiment, the disease or condition is selected from the group consisting of allergy, asthma, and atopic diseases.
In another aspect, the present invention provides a method of treating a disease or condition associated with Th1 cell activity in a patient, the method comprising administering to the patient an antibody that specifically binds to a polypeptide comprising at least about 70% amino acid sequence identity to SEQ ID NO:1.